Gas-collecting method for a steel-making converter

ABSTRACT

A gas-collecting hood is arranged over the circular outlet or mouth of a top-blown steel-making converter. This hood comprises a cylindrical tube or duct with a smaller diameter than the mouth coaxial therewith. The tube is fitted with an outer trough which opens downwardly and sustains a crown vortex feeding back into the main stream. This trough has an outer wall or apron whose diameter is greater than that of the mouth and whose lower periphery is positioned below the bottom end of the tube, while being spaced above the converter.

United States Patent [191 Baumann et al.

[ Oct. 9, 1973 GAS-COLLECTING METHOD FOR A STEEL-MAKING CONVERTER [56] References Cited [75] Inventors: Karl-Friedrich Baumann, Hose]; UNITED STATES PATENTS Halls Hoff Essen-Bredfney, both of 3,372,917 3/1968 Richardson 266/35 Germany; Kurt Braumuller, 3,205,810 9/1965 Rosenak 98/115 R Graz/Osterreich, Austria 3,332,676 7/1967 Namy 266/35 1 Assignees: Gmflried Bischo K p 3,559,975 2/1971 Baumann 2 66/35 $2223: 522%: :T' Essen Primary Examiner-Meyer Perlin g Assistant Examiner-Paul Devinsky Germany; Waagner-Biro AG, Attmey Karl F Ross .y ineetg itiew V [22] Filed: Sept. 29, 1970 y 7 ABSTRACT Ami-9101763647 A gas-collecting hood is arranged over the circular Related Application Data outlet or mouth of a top-blown steel-making con- [62] f S N 78 68 verter. This hood comprises a cylindrical tube or duct 3 :2 2 l9 with a smaller diameter than the mouth coaxial therewith. The tube is fitted with an outer trough which opens downwardly and sustains a crown vortex feed- Foreign Application Priority Data ing back into the main stream. This trough has an Dec. 2, 1967 Germany P 15 83 222.] outer wall or apron whose diameter i greater h that of the mouth and whose lower periphery is posi- [52] US. Cl. 98/115 R, 266/ tioned below the bottom end of the tube while being [51] Int. Cl F23j 11/00, C2lc 5/42 Spaced above the converter [58] Field of Search 98/115 R; 266/35;

. 75/28, 60 1 Claim, 2 Drawing Figures a: if D Cooling 1 11 Apparatus 12 a w a 7 x D" I I T H Air q h I D 3 I T I T T I CO 1 CO GAS-COLLECTING METHOD FOR A STEEL-MAKING CONVERTER This application is a division of application Ser. No. 780,456, filed Dec. 2, 1968 now US Pat. No. 3,559,975.

Our present invention relates to a method of collecting the effluent gases of a steel-making converter.

BACKGROUND OF THE INVENTION Hoods for steel-making converters have hitherto been of two main types. The first and simpler of these types is the one where the hood is merely tightly attached to the top of the converter, sealing the outlet mouth. This system functions we]! to catch all the dustladen carbon monoxide and other noxious gases generated in the converter, and prevents any ambient air from being drawn up the exhaust tube. The sealed junction, however, makes it very difficult to load most types of converters, since they must be tilted for charging and discharging.

A second type allows for a considerable gap between the lower end of the hood and the top mouth of the converter. Such a system makes it easy to move the converter without having to disturb the hood, but presents other notable disadvantages. First of all, it allows the toxic carbon monoxide to escape, to a certain extent, through this gap into the steel plant, thereby endangering plate personnel. On the other hand, a great deal of ambient air is often drawn by the current rising in the hood. A greater quantity of gas must consequently be treated in the subsequent scrubbing and cooling stages. This necessitates a greater processing expense.

OBJECTS OF THE INVENTION It is the principal object of our invention to provide an improved method of collecting gases effluent from a steel-making converter which overcomes these and other common disadvantages.

Another correlative object is the provision of an improved method of collecting the effluent gas from a top-blown converter.

SUMMARY OF THE INVENTION By spacing our hood from the outlet mouth of the top-blown converter thereby allowing the latter to be moved without disturbing the hood, we are able to avoid the disadvantages of earlier systems, if in addition the tube used to draw off the exhaust gas has a diameter which is smaller than that of the outlet mouth of the converter so that only a major central portion of the column of air issuing from this mouth directly enters the tube. Around the lower end of the tube we provide an annular, downwardly opening trough which catches a minor peripheral portion of this column and mixes it with ambient air. The mixture is induced to swirl around in a toroidal or crown vortex in the trough whereby it is finally directed downwardly and inwardly and thence passes into the tube. The lower periphery of the trough is lower than the lower end of the tube (i.e., is closer to the converter) and has a greater diameter than the outlet mouth. Furthermore, the trough may be provided with turbulence-creating elements (i.e., outwardly and upwardly rolled sheet metal baffles) which break the peripheral portion up into a plurality of stacked coaxial toroidal vortices, with possibly different rotational senses.

This vortex or these vortices create a curtain of turbulent gas in the gap between the hood and the con- .verter which both prevents any appreciable amount of carbon monoxide from escaping into the surrounding atmosphere while preventing an undue quantity of ambient air from being caught up and sucked into the tube. In addition, since the effluent gases mayconsist of to percent carbon monoxide in a top-blown converter using oxygen lances, the carbon-monoxide air mixture burns in the crown-vortex trough and thus eliminates part of the need for similar processing of the particle-laden gas which issues from the converter. The gases may then be led to a cooling unit and then a gaswashing and purification installation.

BRIEF DESCRIPTION OF THE INVENTION These and other features, objects, and advantages of my invention will be described in greater detail below, reference being made to the accompanying drawing in which:

FIG. I is a vertical (axial) section through a part of a converter with a hood according to our invention; and

FIG. 2 is a similar section through a second embodiment of our invention.

FIG. 1 shows a top-blown steel-making converter 1 of the Bessemer or Thomas type in a steel-making plant which, in its upright position during the blow, has a mouth 3 opening upwardly and having a diameter D.

Directly above this mouth 3 is a tube or duct 4 for collecting a major fraction of a column of gas rising from this mouth, the tube 4 having a diameter D less than D'. The upper end of this tube 4 is connected to a gas-scrubbing and-cooling plant as shown for example, in the commonly assigned application Ser. No. 668,806 entitled APPARATUS FOR THE RE- MOVAL OF DUST FROM CONVERTER GASES filed Sept. 19, 1967 by Hans Hoff, now US. Pat. No. 3,497,149 one of the present joint inventors. A gascooling device may be interposed. A cooling coil 13 connected to a cooling apparatus 15 limits heat buildup in the tube 4 from damaging it. A lance 2 for blowing oxygen into the converter 1, as is customary for a top-blown converter, enters through a seal 14 and is coaxial with the lower part of the tube 4 and with the mouth 3 in the upright position of the converter.

The hood comprises an annular trough 7 made up of an upper wall 9, an outer wall or apron l0, and an inner wall 11 defining an interior 8. This trough 7 is connected by its upwardly and outwardly divergent generally frustoconical inner wall 11 to the tube 4 at its lower end 6. The outer wall 10 has a diameter D" which is greater than D'. The extreme lower edge of the outer wall 10 is lower than the lower end 6 of the tube 4. The hood is spaced from the mouth 3 by a gap 5.

A column of gas, predominantly carbon monoxide, rising from the mouth 3 is divided into a major central portion which is directly received by the tube 4. Due to the reduced diameter D of the tube 4, a minor peripheral portion is trapped in the interior 8 of the trough 7 and mixed with ambient air to form a toroidal vortex 12. This vortex l2 burns, thereby converting the C0 of the effluent gas into carbon dioxide which passes under the lower end of the tube 4 and rises therein. The vortex 12 serves to burn the carbon monoxide and forms an apron which fills the gap 5 while both preventing too much ambient air from entering the tube 4 and preventing any appreciable quantity of carbon monoxide from escaping.

FIG. 2 shows a slightly different embodiment of our invention where common reference numerals refer to structure common to FIG. 1. Here an inner wall 11 of a trough 7' is bent (into an S-shaped profile) such that an interior 8' of the trough is narrower toward the center than near its top wall 9'. This causes the formation of two vortices l2'a and l2'b which turn in opposite senses of rotation. Such a stack of vortices prevents any gas from escaping or too much air from entering at 5.

The heights 1-! and h of the lower peripheral edges of the tube 4 and the wall 10 and the relative differences between the diameters D, D, and D" determine the size of the vortex 12. This presents only minor problems since the size of the vortex tends to adjust itself to any minor differences in the gap 5 to completely fill it. The combustion taking place in the interior 8 also tends to create a vortex 12 of just the size necessary to maintain an apron of turbulent gas in the gap 5. In addition, momentary differences in the speed of the gas rising from the mouth 3 will not be more likely to lead out the gap 5, but will only increase the speed of the vortex 12 thereby making it even more impenetrable. Preferably D %D' to 60%D'; D" %D' to %D'; D 6h to 7.5h; and H 1.3h to 1.7h.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

We claim:

1. A method of collecting a column of gas issuing from an outlet opening in a top-blown steel-making converter, the method comprising the steps of:

dividing the column into a major central portion and a minor peripheral portion by intercepting said column of gas with an annular wall lying within the outline of said opening whereby the gas surrounded by said wall forms said major central portion and the gas surrounding said wall forms said minor peripheral portion drawing off the major central portion;

mixing the peripheral portion with ambient air and forming a toroidal vortex of swirling mixture around the major central portion while confining said swirling mixture except in the direction of said converter and drawing the swirling mixture off. l 

1. A method of collecting a column of gas issuing from an outlet opening in a top-blown steel-making converter, the method comprising the steps of: dividing the column into a major central portion and a minor peripheral portion by intercepting said column of gas with an annular wall lying within the outline of said opening whereby the gas surrounded by said wall forms said major central portion and the gas surrounding said wall forms said minor peripheral portion ; drawing off the major central portion; mixing the peripheral portion with ambient air and forming a toroidal vortex of swirling mixture around the major central portion while confining said swirling mixture except in the direction of said converter ; and drawing the swirling mixture off. 